1. Field of the Invention
The present invention relates to a packet transport layer apparatus, and more particularly, to a packet transport layer apparatus, which can receive frames having different formats via a single port by dividing a single physical port into a plurality of virtual ports according to each frame format, can increase the number of customer virtual local area networks (C-VLANs) and the number of service VLANs (S-VLANs) being usable at the same time by assigning a different component identifier (ID) to each frame format and using the component ID as a factor used in searching a filtering table, and can translate a frame format to be suited to a frame format allocated to a virtual output port.
2. Description of the Related Art
A packet transport layer, such as transport-multiprotocol label switching (T-MPLS) or provider backbone bridge traffic engineering (PBB-TE), is a packet-based transport layer that receives various Ethernet frames. Specifically, packets are delivered from Ethernet networks in the form of untagged frames, which are basic Ethernet frames, and C-tag frames tagged with virtual local area network (VLAN) tags in 802.1Q. Also, packets from provider bridge networks are delivered in the form of S-tag frames in 802.1ad, and packets from backbone core networks are delivered in the form of B-tag frames in 802.1ah. The edge of a packet transport layer accesses the Ethernet network and the provider bridge network and connects them to the backbone core network. Therefore, the ingress of the packet transport layer needs to translate Ethernet frames (i.e., untagged frames and c-tag frames) and S-tag frames into B-tag frames. In addition, the egress of the packet transport layer needs to translate B-tag frames into Ethernet frames or S-tag frames.
In the packet transport layer according to the related art, a different physical port is allocated to each frame format. Namely, the related art packet transport layer renders only one frame format accessible to a single physical port, and this is disadvantageous in that the Ethernet network and the provider bridge network cannot be connected to the same physical port.
A VLAN identifier (ID) contains 12 bits, and as many as 4096 VLAN IDs may exist in principle. However, the sum of customer VLAN IDs (C-VIDs) and service VLAN IDs (S-VIDs) reaches as many as 4096, and the C-VIDs and the S-VIDs cannot respectively number 4096 in the event that the related art packet transport layer accesses an Ethernet network and a provider bridge network at the same time and uses both C-VIDs and S-VIDs.